As the progress of display technology and every kind of technology craft, various display apparatus have been invented. For example, from compact hand-held displays to high definition display screens or even stereo displays, these displays provide almost-real images. The vivid images with almost-real image quality render human drawing imaginations. The astounding advances and consumption demands for stereo display technology massively grow, such that the quantity of stereo display sold in 2010 reaches a number of millions. While the rapidly decreasing price and the generalization of the contents, stereo display industry would grow fast. However, most of the commercially available stereo displays provide stereo images only when viewers wear special made glasses, such as polarization anaglyph glasses or color anaglyph glasses, which are contrary to human natural visions. Therefore, the auto-stereoscopic technology will become a critical developing trend in the next generation.